[Mpi-comments] MPI_Get_count_x

[Hubert Ritzdorf]

Hi George,

I know MPI_Get_elements_x (). But Page 483 claims:

These functions modify the opaque part of status so that a call to
MPI_GET_ELEMENTS or MPI_GET_ELEMENTS_X will return count. MPI_GET_COUNT
will return a compatible value.

This will not work for large MPI_Count values provided by MPI_SET_ELEMENTS_X
(i.e. MPI_UNDEFINED is returned by MPI_Get_count() in significant use of MPI_SET_ELEMENT_X).
And Page 114 says that function MPI_Get_count has a different behavior than
MPI_GET_ELEMENTS/MPI_GET_ELEMENTS_X. Thus, MPI_GET_COUNT is not obsolete
and application has to develop a separate version of MPI_Get_count_x() if MPI_SET_ELEMENT_X
might be used in the application or a library.

Hubert

________________________________
From: mpi-comments-bounces at lists.mpi-forum.org [mpi-comments-bounces at lists.mpi-forum.org] on behalf of George Bosilca [bosilca at eecs.utk.edu]
Sent: Friday, August 31, 2012 2:26 PM
To: Comments on the MPI Standard
Subject: Re: [Mpi-comments] MPI_Get_count_x

MPI_Get_elements_x, chap Datatypes page 114 (current make cleandoc).

  george.

On Aug 31, 2012, at 13:45 , Hubert Ritzdorf <Hubert.Ritzdorf at EMEA.NEC.COM<mailto:Hubert.Ritzdorf at EMEA.NEC.COM>> wrote:

Hi,

I think, that function

MPI_Get_count_x (const MPI_Status *status, MPI_Datatype datatype, MPI_Count *count)

is missing. After use of function MPI_Status_set_elements_x, MPI_Get_count is possibly not able
to return a compatible value. This is contradictory to Page 483, Lines 22-33.

Hubert



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